Breathalyser tests are used by the police to estimate the concentration of alcohol in the blood by testing alcohol levels in the breath. This is usually measured by noting the colour change in crystals of potassium dichromate. The purpose is to determine whether or not drivers have exceeded legally permitted levels of alcohol consumption. If the test produces a positive result, the driver will then normally be expected to undergo a more accurate breath, blood or urine test. There has been a concerted effort made in recent years to reduce the number of road accidents caused by drink-driving, by a combination of advertising campaigns, random breathalyser tests and driving bans for motorists who test positive. Manufactured by Lion Laboratories plc.